complex ion?

[jana_hahn]

Dear all

(IF4)^n-.

What is the value of n?

I believe it's a square planar, and central atom would be I. I is from group VII, hence, 7 electrons around it. So since there are 4 fluorines, each would share 1 electron with iodine. Which leaves 3 lone electrons, ie, n = 3.

However, answer key says n = 1. Why is that?

Comments

[enchantedskies]

you're looking at charge, not valence electrons.
For a full octet: I only needs 1 bond. But that's not what is happening here...
but you're right, I is the central, its bonded to 4 F, leaving 3 valence electrons, and the shape is square planar. (in this case).
But that's the thing: 3 valence electrons = 1 lone pair and one lone electron. So: two things are going to happen, 1, that electron will be pulled off, giving IF4 a positive charge and leaving one lone pair... (making the shape sawhorse) or it'll gain another electron since e- need to be bonded or paired.
You're question already tells you that it has a negative charge. thus it only gains one electron.

I hope that made sense.